Servo units fob



Oct. 5, 1948. VP. HALPERT SERV O UNITS FOR AUTOMATIC PILOTS Original Filed ua 15. 1942 INVENTOR 'Patented' Oct. 5, 1943' SERVO UNITS FOR AUTOMATIC PILOTS Percy Halpert, Hempstead, N. Y., assignor to The Sperry Corporation, a corporation of Dela- Ware . Original application May 15, 1942, Serial No. 443,146, now Patent No. 2,392,381, January 8, 1946. Divided and this application December 18, 1945, Serial No. 635,'110

v Claims. 1

The present divisional application is based on subject matter `relating to automatic pilots for' aircraft contained in U. S. Letters Patent 2,392,381, issued January 8, 1946.

The primary feature of this invention resides in the centralizing device provided for the control valve parts of the servo unit for the automatic pilot.

invention will be apparent from the following description when read in connection with the accompanying drawing wherein the single 'lgure shows a schematic diagram illustrating, in exploded relation, the Component parts of a servo motor control unit constructed in accordance with the present invention. With reference to the drawing, the servo unit of the automatic pilot is shown to include a controlling torque motor whose stator windings 2! are fed by an electrical signal from an elevator servo amplifler circut of the character particularly described in the copending application of George P Bentley and Carl A. Frische, Serial No. 259,178, filed March 1, 1939, now Patept No. 2,432,502, and not shown herein. The armature 22 of the controlling magnetic motor is mounted to rock about -an axis 23 to position the rocker arm 24 and the respective valves 25 and 26 which arepivotally connected to the arm 24 at' opposite ends of the same by means of the valve stems 21 and 28. The servo unit of the automatic pilot also includes, in the present instance, a three gear type pump, indicated at 29, which is driven by a motor 30 that is energized from a suitable source of electrical energy, as indicated at 3 I. As shown, pump 29 delivers oil or other fluid to the respective valves 25 and 26 by way of fluid circuits or 'pipes 32 and 33, the return flow of the fluidto which the valves ofier but small resistance in their normal positions being made by way of the common pipe 34, sump 35.an.d pump intake pipes 36 and 31. The outlet pipes of the pump 29 also communicate with the respective ends of a servo cylinder 38. such connection is accomplished as shown by the respective pipes 40 and 4I. It will be understood that movement of pistons 43 results from a change in the normally balanced pressure in opposite sides of the main servo cylinder 38. Control over the servo unit is exercised by the torque motor whose coils or windings 2l are connected across the output of an ampliflercircuit which normally applies the same voltage across each coil. The magnetic armature 22 consequently is afiected by equal and opposite torque and therefore exerts no force to tend to close Other features :and structural details of the 2 either of the valves 25 or 26. When the signal for the torque motor is unbalanced, the armature 22 is rocked and the valves 25 and 26 moved correspondingly which differentially restricts the free flow of fluid from the pump 29 through the valves' and sump 35 back to the pump. The pump consequently builds up a pressure to overcome the restrction caused by unbalancing of the valves which results in the controlling movement of the pistons 43. Piston movement of the main cylinder 38 is communicated directly to drum !5 by way of the piston connecting rack '44, pinion 45 and driving shait 46.

When automatic flight control is not required, it is desirable that the pilot be able to eflect manual movement of the pistons 43 without opposition since the rack engaging pinion 45 for .pistons 43 is mechanically connected to the craft's cable system I 4. In accordance with the' teaching of the present invention such a result is obtained without using an additional oil by-pass by a means for centralizing the differential controllng valves and 26 of the servo unit. As shown, means 'are provided in the form of a forked arm 41 whose 25 spread ends engage the undersurface of two spaced blocks 48 rigidly mounted on the rocker arm 24. Engagement of arm 41 with blocks 48 is eifected by means of spring 49 which urges the spring 49 and permit the servo motor to respond to signals for automatic flight. When the circuit to the pump motor 30 is opened, the pump ceases functioning and'the solenoid 50 is no longer enerv gized, which restores the system to the control of the spring 49 which is then effective to centralize the rocker arm 24 with the valves 25 and 26 in their full open position, the effect of the spring overcoming in a positive manner the torque motor armature to which the arm 24 is directly connected. This permits the fluid to by-pass freely through the control valves as soon as the power tothe pump drive motor is removed. Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawcomprises a spring.

ing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In automatic piiots for aircraft having an hydraulic servo unit supplied by a continuousiy Operating pump and operated through two fluid circuits controlled by dififerentially movable valves mounted on a rocker arm, automatic means operable through the arm for moving thevalves from a central position to unbalance the fluid circuits, normally inefiective means for positively centralizing the rocker arm of the valves. and means for rendering said centralizing means effective upon stoppage in the continuity of operation of the pump.

2. In automatic pilots for aircraft having an hydraulic servo unit supplied by an electricaliy driven. continuously Operating, pump and opera-ted .through two fluid circuits controlled by ditferentialiy movabie valves mounted on a rocker arm, a torque motor for moving the valves by way of the rocker arm from a central position to unbalance the fluid circuits, automatic means for controlling said torque motor, normally ineffective means for positively centraiizing the rocker arm of the valves, and means for rendering said centralizing mean-s eflective upon disablement of the electric supply to the pump.

3. An automatic pilot for aircraft. as claimed in claim 2, in which the normally ineflfective means for positively centralizing the rocker arm 4. An automatic pilot for aircraft, as claimed' in claim 2, in which the means for rendering the centralizing means effective comprises -a solenoid.

5. An automatic pilot for aircraft having a fluid servo unit supplied by a motor jiriven, continuously Operating, pump and operated through two fluid circuits 'controlled by diiferentially movable valves mounted on a rocker arm, a torque motor for moving the valves by way of the rocker arm from a central position to unbalance the fluid circuits, automatic means for controlling said torque motor, a normally ineifective spring for positively centralizing the rocker arm of the valves, a motor circuit, and a solenoid. situated in said motor circuit, operable to rende'r said spring effective when said circuit is opened.`

PERCY HALPERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,398,421 Frische et .al Apr. 16, 1946 FOREIGN PATENTS Number Country Date 538,526 Great Britain Aug. 7, 1941 

